1. Field of the Invention
The present invention relates generally to a mixer harmonic calculator for use with database search systems for high frequency electronic components. More specifically, the invention relates to rapid and efficient online parameter-based database search and calculation systems for mixers and mixer harmonics performance utilizing actual measured performance data as well as optional interpolated and otherwise calculated data; wherein the calculation results also provide the user with the option of obtaining output data including tabular and graphed depictions of mixer performance over the range of operating parameters input.
2. Description of the Prior Art
Engineers designing circuits in the radio frequency (RF) and microwave range have to search through published and online data sheets, online databases and assorted formats of catalogs in order to find appropriate components to match to specific applications. Engineers have to search through an enormous amount of data to find the best component for a particular requirement, and even the experienced high-frequency design engineer is challenged to understand how some components can fit into a circuit or system better than others. Mixers are one type of high frequency circuit where the difference between calculations approximated from ideal models and calculations based on actual measured circuit performance can strongly affect eventual circuit performance.
As used herein, radio frequency is taken to mean the high frequency portion of the electromagnetic spectrum, from at least 3 MHz. Microwave is taken to mean frequencies from at least 300 MHz.
In some design circumstances, a high frequency design engineer will choose to select a component with broader-than-needed general performance characteristics in order to gain improved performance in one or more parameters over a narrower frequency range. For example, rather than simply selecting a double-balanced mixer with RF and intermediate frequency (IF) ranges to translate a desired signal band, the engineer may use broader-band mixers over narrower portions of their range to meet a required linearity specification, or conversion-loss level, or optimum local-oscillator (LO) drive level. This illustrates the basic complexity of design choices made in selecting high frequency electronic components. For mixers in particular, there is a further set of challenges in analyzing the effects of higher order harmonics on circuit performance and signal output. The prior art databases are limited to having actual known harmonic frequencies used in calculations with theoretical “ideal” models, rather than with actual measured data. These “ideal” models are very simplistic and don't include real-world performance effects from the balun circuits, internal balancing networks or from package-induced effects.
Component searches are increasingly performed over highly distributed computer networks due to the ready availability of the World Wide Web and high-speed Internet access, coupled with ever-improving software and server technology for powering content-rich websites. Online (web-based) catalogs represent one class of computer databases, with online catalogs containing parametric data being a significant subset of those. A further significant subset of this type of catalog allows the user to enter choices for a variety of component parameters to search for at once, to aid in efficient searching for a particular component to be appropriate for use under specific performance conditions. Some catalog database search systems of this type also allow the user to perform a limited range of performance simulations as well.
The majority of online catalogs are based on a server-side system, where the user's machine is not performing any calculations or storing any data. Generally such a system is providing the catalog database function to a large number of users at once and the database is very large, so it is imperative that the system be designed to provide a sufficient quality of data at a speed that the user will find acceptable.
The Yoni-1 catalog database system is an example of a prior art online catalog search system containing a considerable body of parametric data for a large number of high frequency electronic components. Users are able to access the catalog through standard web browser software and search for specific components with input variables including frequency range and other electrical performance characteristics, as well as package type. The search output lists the components in the catalog that match the user's search request.
While this type of system offers considerable benefit over simple tabular or graphed listings of devices and their relevant parameters, the search process frequently involves numerous iterations of guessing and refining entered data to gain a match with the component parametric data stored in the database. Further, the selection of high-frequency electronic components requires accurate information about the exact performance of the components under specific conditions of signal input and circuit application.
U.S. Pat. No. 6,334,115 entitled COMPONENT ELECTRONIC CATALOG teaches an electronic component database system intended to aid in selecting and identifying components in a context of circuit design for improved placement during pc board assembly, wherein the stored data includes text-based information about the components, images of the components, mechanical package details and other data relevant to the preparation of automated or semi-automated picking and placing of components. This system is optimized for improving the assembly of components onto pc boards, but has no parameter-based search capabilities for the selection of components for basic circuit design.
U.S. Pat. No. 6,484,169 entitled SELECTION AND ORDERING OF LAMP COMPONENTS teaches an online catalog search system that has a prioritization scheme for a number of component attributes, wherein the user enters a numerical ranking for the importance of each attribute in the context of their specific application. Additionally, if no exact match is achieved with the entered parametric data, data ranges and prioritized attributes, the system informs the user of the no match condition and presents the option of viewing the components in the database that are judged to be closest to the user's criteria. This may lead the user astray, especially if there have already been several frustrating search iterations. There is also no provision for prioritizing the parametric data or data range entries, or for performing any device simulation or analysis.
The Yoni2 database search system offers significant improvements over the prior art, as taught in two patent applications. Patent application Ser. No. 11/648,238 entitled DATABASE SEARCH SYSTEM USING INTERPOLATED DATA WITH DEFINED RESOLUTION teaches a parametric database system capable of interpolating between actual measured data points to further populate the database with interpolated data, capable of limiting data resolution to a desired level to prevent overuse of memory and processing resources, and of redefining the resolution defined by the user to be no greater than the set resolution programmed into the system. Patent application Ser. No. 11/731,244 entitled DATABASE SEARCH SYSTEM FOR HIGH FREQUENCY ELECTRONIC COMPONENTS teaches a high frequency component search system allowing users to perform an online search within a given product category based on their own specifications, but with component-specific guidance about which parameters are generally more important within the context of the database. The Yoni2 system uses highly optimized search algorithms to return search results rapidly, and when the search fails to achieve a data match, offers the option of prioritizing one or more parameters in the process of refining the entered parameters for a next search iteration. While the current Yoni2 database system is more capable than earlier database search systems for locating and specifying high speed electronic components, the selection of mixer components would be greatly improved by the capability to analyze accurate harmonics data for specified LO and RF input frequency ranges.
Software tools to predict and display M×N order LO and RF mixing products are well known in the art. There are also software tools to estimate the amplitude of mixer output signals based on the input signal levels, using mathematical models for the nonlinear elements of the mixer to predict the amplitude of mixing products including the harmonics. Some of these tools for calculating mixer harmonics, also known as mixer spurious products or “spurs”, are available online. However, these software tools are based on ideal conditions, not on real-world use of mixers. To achieve isolation, most mixers are designed in a balanced configuration such that the signal ports of the mixer include baluns to drive the internal semiconductor mixing structure. Typically the balun structure is composed of diodes or Field Effect Transistors (FETs). These balun structures at the mixer ports present impedances that vary as a function of frequency and this impedance change affects the amount of harmonic content generated in the mixer as well as how much harmonic energy enters or leaves the mixer ports such that the harmonic termination very far out of the input frequency band will affect the mixing products generated in the frequency band. Thus, the termination presented to the nonlinear semiconductor elements both in and out of the frequency band will affect performance within that frequency band. The baluns, plus any internal matching networks and the high-frequency parasitic effects of electronic packaging all serve to deviate actual circuit performance from ideal models.
Given the inherent tradeoffs between bandwidth, performance, size and cost, there are many mixer configurations available for different frequency ranges, bandwidths and LO levels. Every mixer circuit has a unique set of performance parameters based on the actual circuit, including the type of semiconductor devices used, the balun structures, the matching networks, and the electronic packaging. Unless actual measured data is used to characterize the performance of a given mixer, any performance calculations will be approximate at best.
A more capable mixer harmonics calculator would have means for interpolating between actual measured data points and calculating M×N order harmonics frequencies and amplitude in response to specified bands of LO and RF input signals. Further, the mixer harmonics calculator would enable display of database search and calculation results in tabular and graphed formats allowing optimization of data viewing for selected frequency ranges. A more capable high frequency electronic component database search system would include a mixer harmonics calculator utilizing actual measured data for each mixer component, including measurements of effects from real-world components such as mixer baluns and balancing networks, and the high frequency effects of electronic packaging.